Somehow when I first started learning about radio and electronics, someone explained how complicated equipment like radiograms and tape recorders were made from simple building blocks that I was capable of understanding and building for myself.
What drove me to do it was the fact that I could not afford a hifi or radio control equipment, so building was the only option. or more likely, repairing a busted system reclaimed from the trash.
So how does that play today?
Can today's kids see the stepping-stones between what they can make with their own resources, and the gadgets that they desire? I doubt it, with the exception of software, woodwork and cookery. I don't see any kid putting an MP3 player together from secondhand parts.
Repairing one, though, possible if it's just a dry joint (need good eyesight though).
Many or most can afford to buy stuff outright, even if they are arts students with no technical interest, they can listen to music or surf on their iPads and phones. Items that parents regarded as essential times for a happy life are bought for them.
What were the essential items my folks bought for me? School clothes, Sunday best clothes, shoes, food, a penknife, a secondhand bicycle, a watch (eventually). Everything else was down to me saving birthday and Xmas money and working for the rest.

Let's face it, STEM isn't appealing to every teenager -- although the electronic gadgets that result from STEM certainly are. Perhaps these kids were unwilling participants, dragged along on a school field trip. If not STEM, then hopefully there is something, anything, that sparks their interest and curiosity to learn.
Your piece reminded me of the opening verse of the Kaiser Chiefs song, "Never Miss A Beat":
What did you learn today?
I learned nothin
What did you do today?
I did nothin
What did you learn at school?
I didn't go
Why didn't you go to school?
I don't know
It's cool to know nothin...

I reckon the problem was bigger than you alone could fix, Naomi. You're probably right about getting them alone, I remember types like this from my schooldays. It's sad that sometimes peer pressure is so powerful. But sooner or later these kids will find themselves in the big bad world and that the others they hang with don't help them. Then either they'll come right or get into gangs. I don't know what you can do about it either. Good luck.